Lubricant composition for the bearings of the cutters on a roller earth-boring drill



June 8 1926. 1,587,944

LUBRICANT COMPOSITION FOR THE BEARINGS OF THE OUTTERS ON A ROLLER w. FLETCHER .m2 I9 R1 D I 5 I l mm BJ Hd Re n An H EF /wW/n E? HW. FLETCHER INVENTOR.

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Patented June 8, 192,6.

UNITED STATES PATENT OFFICE.

HAROLD W. FLETCHER, OF HOUSTON, TEXAS, ASSIGNOB T0 HUGHES TOOL COMPANY, I

OF HOUSTON, TEXAS', A CORPORATION OF TEXAS.

LUBRICAN T COMPOSITION ron THE BEARINGS or THE cUTrEas' oN A ROLLER italiani-iaoimzel DRILL.

'Application tiled J'anuary25, 1921. Serial No. 439,738.

My'invention relates to a lubricating composition for especial application to rotary earth boring drills of the roller type. In such devices the drill bits used have cutting.v rollers on the forward end thereofj that are adapted to roll on the bottom of the hole and, act t disintegrate the material. Streams of lushin fluid are pumped down from the surface irough the hollow drill stem to whichthe bit is attached.` This fluid is discharged through channels in the head of the bit upon the `cutters andserves to wash away the disintegrated matter and carry it in sus nsionup loutside the drlll stem to the sur ace where it is discharged.

The rolling cutters which act to drill the hole are under heavy strain and also operate under the pressure of a head of mud inthe hole. The type of lubricator best adapted to work under these conditions is disclosed in Hughes Patent No. 930,759 issued Au ust 10, 1909. The head of water in the stem is slightly in excess of the Ahead of` rill water outside ofthe drill stem due to the pressure of the pumps and to the dammmg -up of the water in the drill stem by the relatively small passages in the head of the.

bit through which the flushing fluid is discharged. This excess pressure is exerted upon the lubricant. vin its container and` serves to force it to the bearings against the slightly smaller head of fluid pressure outside-the drill stem.

` The diiiculty with this method of lubrication is that it is rather diiiicult to `fit a plunger over the lubricant in its container which will move freely and still be tight enough to prevent the muddy flushing fluid,

which drives the lubricant, fromfleaking,

in roller earth boring drills so that the mud will not mix with the lubricant and pass'y therethrough to the bearings.

Another object is to prevent the mixture of the flushin fluid, used with earth boring drills, with e lubricant by making the lubricant of heavier specific gravity. than the iiushing fluid.

Referring tothe. drawings, I have illustrated in Fig.. 1 a view, partly in central longitudinal section, showing a roller drill in which ordinary lubricant is used. Fig.

,2 is a similar view in which the eii'ect of my improved method of lubrication is shown.l f

Like numerals of reference apply to like parts in both the views.

The Adrill 1 is shown in the drawing as having roller cutters2 on the forward end f thereof.' .The drill is attached by means of a drill collar 3- to a drill stem 4 by means of which it is rotated .by mechanism at the surlface-of the ground.` i

. A lubricator, consisting of a barrel 5 of relatively small diameter, is secured to a nipple 6 onv the upper shank of the bit. Passages or oil ducts, not shown, lead from vthe lubricator through the head to the bear' ings of the drill as shown in the Hughes Apatent previously referred to. The upper end of the lubricator is closed by a plug 7 low the plug, openings 8 allow entrance of flushing Huid tothe cator barrel. K Within the lubricator a plungerv9 vrrests upon the upper surface of the lubricant 10 and serves to transmit the pressure of the flushing fluid to the lubricant to force said lubricant to the bearingsl of the cutters.

'screwed internally within thebarrel. Be-

interior of the lubl- In the operation of the device as shown in Fig. 1 the lubricant is a hea Agrade of lubricating oil. No specific grae of lubricant is required, but I haye used an oil having a specific gravity of about 0.9, a ash point of approximately 400 Fahrenheit, and a viscosity of around 500 Saybolt, or over. The spots 11 indicate small masses of the iiushing fluid which have been forced past the plunger and the masses are slowly sinking to the lower end of the lubricator end to the bearings of the cutters.

To avoid this mixing of the mud with the oil, I contemplate compounding with the lubricant a pulverized heavy mineral substance such as lead oxide or barium sulfate,

which will sta in ,sus ension 1n the lubricant and wil not a ect the lubricatin qualities of the oil. This mixture of lubricant and heavy mineral will have a eater specific gravity than the flushing ilui For this reason, if the flushing fluid works past the plunger, it will still stay on top of the lubricant as indicated in Fig2 and will not affect the lubrication of the cutter bearin until the lubricant itself has been entire y exhausted. As it is possible to regulate the size of the lubricator and the quantity of y lubricant therein to provide an amount suiicient to run for the desired length of time, no trouble with muddy-lubricant will be experienced. Barium sulfate is especially adapted for mixing with the lubricant. It remains readily in suspension and is of high molecular weight. Furthermore it does not affect the lubricating qualities of the oil sult disastrously. It is only necessaryto mix with lthe lubricant a suitable proportlon of the heavy mineral in the manner de-' scribed and the greater'specific gravity vof the lubricant will prevent the mixture therewith of the flushing mud and thus prevent wear on the bearings.

Having thus described my invention, the advantages of which will beapparent to one skilled in the art, what I claim as new and desire to protect by Letters Patent is:

A lubricant for the bearings of the cutters on a roller earth-boring drill in which a muddy fluid is used in forcing the same t0 the bearings, consisting of a mixture of heavy grade lubricant with a heavy pulverized mineral. substance in quantities suicient to raise the specific gravity above that of saidv muddy fluid.

In testimony whereof,I -I hereunto afiix my signature, this the 15th day of January, A. D., 1921.

HAROLD W. FLETCHER. 

